The present invention relates to an airbag of an airbag device mounted in a vehicle, and particularly to an airbag which includes an internal pressure adjusting mechanism which can adjust an internal pressure of the airbag by exhausting a flowed-in inflation gas or by suppressing the exhaust.
In the related art, an airbag of an airbag device is known which uses a tether in an internal pressure adjusting mechanism (for example, see JP-A-2008-207579 and U.S. Pat. No. 7,328,915). In the internal pressure adjusting mechanism, when the inflating airbag protrudes from a housing portion, and an occupant approaches the housing portion, the inflation gas is exhausted from an exhaust port of the internal pressure adjusting mechanism to suppress the internal pressure increase of the airbag and to prevent that the airbag strongly abuts on the approaching occupant. In addition, when the occupant is in a proper position where the occupant does not approach the housing portion, the exhaust of the inflation gas is suppressed such that the airbag is completely inflated rapidly. The internal pressure adjusting mechanism is configured such that the peripheral edge of the exhaust port provided in an inflating bag part is formed in a tube shape, and a predetermined length of the tether extending from the inside of the bag part is coupled with the tube portion.
In the internal pressure adjusting mechanism, when the bag part of the airbag is inflated in a state where the occupant approaches the housing portion, the bag part interferes with the occupant in a state where the tether is loosened before the inflation of the bag part is completed, the tether remains in the loosened state, and the tube portion of the exhaust port is maintained to be opened. For this reason, the inflation gas is exhausted from the opened exhaust port, and the inflation of the bag part is suppressed, so as to reduce the force that the bag part presses the approaching occupant. On the other hand, when the occupant is positioned in the proper position where the occupant does not approach the housing portion, the bag part of the airbag protrudes smoothly from the housing portion, so that the tether is stretched. For this reason, the tube portion of the peripheral edge of the exhaust port is stretched by the tether to enter into the bag part, and further the tube portion is crushed by the internal pressure of the bag part to close the exhaust port. Thus, the exhaust of the inflation gas from the exhaust port is suppressed so that the inflation of the bag part is completed rapidly.
However, the airbag in the related art is configured such that, in the state of the exhaust suppression mode, a cylindrical tube portion which is pulled in the bag part is crushed by the internal pressure of the bag part, so as to close the exhaust port. The crushed state indicates a state where the circumferential wall of the tube portion is gathered to the center side. Thus, an occurrence of a wrinkle cannot be avoided so as to be gathered to the center side, whereby the leakage of the inflation gas from the gap of the wrinkle cannot be prevented. Particularly, when the opening area of the tube portion is widened to maintain the stable exhaust mode, the length of the circumferential wall of the tube portion in the circumferential direction is further increased. Thus, during the exhaust suppression mode, the wrinkle which occurs when the tube portion is gathered to the center side is increased, so as to further promote a gas leakage. For this reason, in the configuration of the airbag in the related art, although the state is shifted to the exhaust suppression mode, the leakage of the inflation gas occurs. Thus, there is a problem in ensuring a stable exhaust suppression state of the exhaust suppression mode.